Photoelectric-Photothermal Synergistic Enhanced Photo-Assisted Zinc-Ion Batteries based on Carbon-Coated Hydrated Vanadium Oxide

Abstract

Photo-assisted zinc-ion batteries (PAZIBs) can utilize sunlight to enhance aqueous Zn2+ storage, yet their practical performance is often limited by sluggish interfacial charge transfer and insufficient light utilization. Herein, we report a carbon-coated, K⁺-intercalated hydrated vanadium oxide (Cx-KVOH) photocathode for efficient photo-assisted Zn2+ energy storage through synergistic photoelectric and photothermal enhancement. By introducing carbon-layer-assisted photothermal regulation into the KVOH, this work extends photo-assisted Zn²⁺ storage from a mainly photoelectric enhancement mode to coupled photoelectric-photothermal enhancement. In this design, the carbon layer simultaneously improves electronic conductivity, promotes photogenerated charge separation, enhances structural stability, and serves as a photothermal medium for light-to-heat conversion. Therefore, the assembled PAZIBs achieve a high discharge capacity of 386 mAh g-1 at a large current density of 5000 mA g-1 under one-solar illumination, which is 21% higher than under dark conditions. This improvement is attributed to the synergistic effect of photothermal and photoelectric effects, which accelerate charge transfer and Zn2+ diffusion kinetics. Furthermore, the device retains 91% capacity after 4000 cycles, thanks to the participation of photogenerated carriers in the reaction and the significantly improved structural stability provided by carbon coating. More importantly, under an ambient temperature of -6 °C, the carbon layer converts incident light into heat and raises the local working temperature of the cell, thereby alleviating low-temperature kinetic limitations and enabling enhanced Zn2+ storage. Our work offers new insights for designing high-performance PAZIBs and enhancing their environmental adaptation.